Water heater system, especially for motor homes

ABSTRACT

A water heater system, especially for motor homes, includes a heater ( 12 ) with a heat exchanger arrangement ( 16 ) for transferring heat from the heater to a first heat carrier medium, a water reservoir ( 32 ) for water to be heated and a heat transfer arrangement ( 30 ) for transferring heat in the first heat carrier medium to water in the water reservoir. The heat transfer arrangement includes a heat exchanger tube ( 34 ) with a heat coupling area ( 36 ) for thermal interaction with the first heat carrier medium and a heat decoupling area ( 38 ) for thermal interaction with the water. The heat exchanger tube has a first flow space area ( 54 ) for essentially gaseous second heat carrier medium flowing from the heat coupling area to the heat decoupling area and a second flow space area for essentially liquid second heat carrier medium flowing from the heat decoupling area to the heat coupling area.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2011 004 599.6 filed Feb. 23, 2011, the entire contents of which are incorporated herein by reference

FIELD OF THE INVENTION

The present invention pertains to a water heater system as it can be used especially in motor homes.

BACKGROUND OF THE INVENTION

In general, fuel-operated heaters, which are supplied with diesel fuel or heating oil, are used, in general, in such motor homes to heat the interior space of the motor home. Gas, which is kept ready in the form of gas tanks, is used, in general, to produce hot water and also for cooking.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a water heater system, which can be operated with the same fuel as that used to heat air to be introduced into the interior space.

This object is accomplished according to the present invention by a water heater system, especially for motor homes, comprising a heater with a heat exchanger arrangement for transferring heat generated in the heater to a first heat carrier medium, a water reservoir for receiving water to be heated and a heat transfer arrangement to transfer heat being transported in the first heat carrier medium to water in the water reservoir, wherein the heat transfer arrangement comprises at least one heat exchanger tube with a heat coupling area that is or can be brought into thermal interaction with the first heat carrier medium and with a heat decoupling area that is in thermal interaction with the water, wherein a second heat carrier medium is contained in the at least one heat exchanger tube, and a first flow space area is formed essentially for the flow of gaseous second heat carrier medium flowing from the heat coupling area to the heat decoupling area, and a second flow space area is formed essentially for the flow of liquid, second heat carrier medium flowing from the heat decoupling area to the heat coupling area.

Heat is provided in the water heater system according to the present invention in a heater, i.e., especially a heater supplied with liquid fuel, in order to be transferred to a first heat carrier medium. This first heat carrier medium may be the air that is also to be introduced into the interior space of the vehicle. The heat carrier medium may release or transfer part of the heat being transported therein in the area of the heat transfer arrangement to the second heat carrier medium present in the at least one heat exchanger tube, namely, in the heat coupling area of this at least one heat transfer tube. The second heat carrier medium evaporates in the heat coupling area due to the absorption of heat. Due to the flow pressure conditions present or building up in the heat exchanger tube, the gaseous first heat carrier medium flows in the direction of the heat decoupling area in the first flow space area. Since this the heat decoupling area will also have a lower temperature than the heat coupling area at least when the water container in the water reservoir has a comparatively low temperature, the second heat carrier medium condenses in the heat decoupling area. The heat being released during the condensation is transferred in the heat decoupling area towards the outside to the water surrounding this heat decoupling area, so that heating of the water takes place.

Highly efficient heating of the water is made possible by the use of at least one such heat exchanger tube to transfer heat from the first heat carrier medium to the water to be heated, because such a heat exchanger tube has a very high heat transport capacity, since it utilizes the physical effect of energy release during condensation, i.e., during the phase transition from a gaseous to a liquid state.

To guarantee efficient flow of the first heat carrier medium about the heat coupling area, it is proposed that a delivery means for delivering first heat carrier medium from the heat exchanger arrangement through a heat carrier medium duct to the heat transfer arrangement be provided.

If the delivery means comprises a heating air blower, the first heat carrier medium can be used with one and the same delivery means both to heat the interior space, for example, of a motor home, and the water contained in the reservoir.

To further support a defined flow of the heat coupling area about the at least one heat exchanger tube, it is proposed that at least one heat exchanger tube extends, at least in its heat coupling area, essentially at right angles to a direction of flow of the first heat carrier medium in the area of the heat transfer arrangement. As an alternative or in addition, provisions may be made for the at least one heat exchanger tube to extend at least in its heat coupling area essentially in parallel to a direction of flow of the first heat carrier medium in the area of the heat transfer arrangement.

To obtain an embodiment of the heat transfer arrangement that can be embodied with a simpler construction, it is proposed that at least one heat exchanger tube extend essentially straight over its entire length.

As an alternative, provisions may be made for the at least one heat exchanger tube to be curved in a transition area. The direction in which the at least one heat exchanger tube extends for absorbing heat from the first heat carrier medium (heat coupling), on the one hand, and for transferring heat to water (heat decoupling), on the other hand, can be selected in this manner independently from one another.

Furthermore, to increase the quantity of heat that can be transferred to the water to be heated, it is proposed that a plurality of heat exchanger tubes, which extend in parallel to one another at least in some areas, be provided. Provisions may be made now for at least some of the heat exchanger tubes to be offset in relation to one another in their heat coupling area in the direction of flow of the first heat carrier medium in the area of the heat transfer arrangement or/and at right angles thereto.

It is proposed in an especially advantageous variant that the second heat carrier medium have a condensation temperature in the range of 60° C. in at least one heat exchanger tube. It can be achieved in this manner that if the temperature of the water comes close to 60° C., the thermodynamic process becomes more inefficient in the at least one heat exchanger tube, i.e., less heat is extracted in the case of the first heat carrier medium even if it has a temperature that is markedly above 60° C.

It may, furthermore, be advantageously proposed in the water heater system according to the present invention for the heater to be operated with fuel and to have a burner area to receive preferably liquid fuel and combustion air and to burn a fuel/combustion air mixture. This makes it possible, for example, to feed the water heater system with the same liquid fuel that is also used to operate the motor home, i.e., for example, diesel fuel.

To be independent from the position in which the water heater system is installed relative to the direction of the force of gravity during the operation of the water heater system, it is proposed that the second flow space area be provided, at least in some areas, with a material having capillary structure. The second heat carrier medium condensing in the heat decoupling area can thus be absorbed in the material having capillary structure and flow, due to the capillary delivery effect of that material, in the direction of the heat coupling area, where it can evaporate due to the introduction of heat taking place there and thus leave the material having capillary structure.

The present invention will be described below in detail with reference to the figures attached. In the drawings. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a water heater system according to the present invention;

FIG. 2 is a longitudinal sectional view of a water reservoir in connection with a heat transfer arrangement;

FIG. 3 is a partially cut-away cross-sectional view of the assembly unit shown in FIG. 2;

FIG. 4 is a sectional view of the assembly unit from FIG. 2, cut along a line IV-IV in FIG. 2;

FIG. 5 is a partially cut-away view of a heat exchanger tube;

FIG. 6 is a simplified schematic view corresponding to FIG. 2 of an alternative embodiment;

FIG. 7 is a simplified schematic view corresponding to FIG. 2 of an alternative embodiment; and

FIG. 8 is a simplified schematic view corresponding to FIG. 2 of an alternative embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in particular, a water heater system that can be used, for example, in a motor home, is generally designated by 10 in FIG. 1. The heater system 10 comprises a heater 12 to be operated with liquid fuel with a burner area 14 and with a heat exchanger arrangement 16. Liquid fuel is fed from a fuel reservoir 20 to the burner area 14 by a fuel feed arrangement, for example, a metering pump 18. The heat generated in burner area 14 is transferred to the heating air L_(H) used as a first heat carrier medium in the area of the heat exchanger arrangement 16. This heating air is delivered by a blower, which is generally designated by 22 and which comprises a first delivery area 24 essentially for delivering the heating air and a second delivery area 26 for delivering combustion air LV to be introduced into the burner area 14.

It shall be pointed out here that separate blowers, operated independently from each other, may, of course, also be provided for the heating air and the combustion air.

The heating air L_(H) heated in the area of the heat exchanger arrangement 16 during the combustion operation of the heater 12 flows through a heating air duct 28 in the direction of a heat transfer arrangement generally designated by 30. In the area of this heat transfer arrangement, the heating air L_(H) releases part of the heat being transported therein. This is transferred to the water contained in a water reservoir 32 in the manner described below. The heating air L_(H) then flows farther with reduced temperature and can be introduced, if necessary or desired, into the interior space of, for example, a motor home, in order to heat this or, if this is not necessary or desired, it can be released to the outside.

The heat transfer arrangement 30 shown in more detail in FIGS. 2 through 4 comprises a plurality of heat exchanger tubes 34 extending essentially in parallel to one another. These are located with a respective heat coupling area 36 in the heating air duct 28 and are located with a respective heat decoupling area 38 in the interior space 40 of water reservoir 32, which said interior space is filled, in general, with water.

To enlarge the total surface available for transferring heat to the heat exchanger tubes 34 in the heating air duct 28, these heat exchanger tubes 34 may be coupled with essentially flat, large-area heat transfer elements (e.g., fins) 42 elongated in the direction of flow R in their heat coupling areas 36 extending essentially at right angles to the direction of flow R of the heating air L_(H) in the area of heat transfer arrangement 30. These heat transfer elements 42 may comprise, for example, corresponding to the circular outer circumference of the heat exchanger tubes 34, cylindrical connection attachments 44, into which the heat coupling areas 36 are introduced and stationarily inserted, for example, by material connection or by press fit. As this is shown clearly in FIGS. 2 and 3, a plurality of such heat transfer elements 42 may be arranged one on top of another in their respective heat coupling areas 36 in the longitudinal direction in which the heat exchanger tubes 34 extend.

As is shown in FIG. 4, the heat exchanger tubes 34 may be located, in relation to one another, in the direction of flow R and offset at right angles thereto. For example, a plurality of rows of heat exchanger tubes 34 extending essentially in the direction of flow R may be provided, wherein the heat exchanger tubes 34 at least two rows directly adjacent to one another are located offset in relation to one another in the direction of flow R, so that, for example, a heat exchanger tube 34 of a directly adjacent row is located, for example, between two heat exchanger tubes 34 of one row approximately in the middle in the direction of flow R.

The heat exchanger tubes 34 absorb heat from the heating air L_(H) in their respective heat coupling areas 36 and transfer this in the direction of the respective heat decoupling areas 38. The heat is again released there and transferred to the water container in interior space 40.

The thermodynamic mechanism by which this heat transfer takes place in the heat exchanger tubes 34 will be explained below with reference to FIG. 5.

FIG. 5 shows a heat exchanger tube 34 such that its heat coupling area 36 is located on the left and its heat decoupling area 38 on the right. Heat exchanger tube 34 is built with an essentially cylindrical, comparatively thin outer circumferential wall 46 made, for example, of a metallic material. The heat exchanger tubes 34 are closed by respective bottom walls 48, 50 in their longitudinal direction, so that an essentially fully encapsulated inner volume is obtained. This inner volume contains a second heat carrier medium, which is designed in terms of its thermodynamic properties such that, taking into account the pressure conditions prevailing in the inner volume of the heat transfer area at the temperatures relevant in this application, it has a phase transition between a gaseous state of aggregation and a liquid state. For example, the design may be such that at an inner pressure of about 10-5 bar, the condensation temperature of the second heat carrier medium is about 60° C. For example, NH3 may be used for this as the second heat carrier medium, and the vacuum in the heat exchanger tube 34 can be adjusted correspondingly to set the condensation temperature.

A cylindrical capillary structure element 52, which extends with its cylindrical structure from the heat coupling area 36 to the heat decoupling area 38, is provided in the interior of the heat exchanger tube 34, for example, in contact with the inside of the outer circumferential wall 46. The capillary structure element 52 is hollow on the inside and thus surrounds a first flow space area 54, in which gaseous second heat carrier medium can flow from the heat coupling area 36 to the heat decoupling area 38. The gaseous second heat carrier medium is generated in the heat coupling area 36 when heated heating air L_(H) flows about this area and a heat flux WE is transferred to the second heat carrier medium contained in the capillary structure element 52 in the liquid state. The second heat carrier medium is heated above its condensation or evaporation temperature and is discharged from the capillary structure element 52 to the inside in the gaseous state and thus enters the first flow space area 54. Based on the fact that gaseous second heat carrier medium is formed in the heat coupling area, an overpressure is present there, so that, promoted by the pressure difference generated from the heat decoupling area 38, the gaseous second heat carrier medium flows from the heat coupling area 36 to the heat decoupling area 38.

The heat exchanger tube 34 is in contact in the heat decoupling area 38 with the even colder water, which has a temperature below the condensation temperature of the second heat carrier medium. Heat exchanger tube 34 will thus also have a correspondingly low temperature in this area, which causes condensation of the gaseous second heat carrier medium in the heat decoupling area 38 and entry of this heat carrier medium into the capillary structure element 52 due to the capillary structure or capillary delivery effect of said capillary structure element 52. The heat of condensation being released during the condensation is transferred into the water as heat flux W_(A).

Due to the loss of liquid second heat transfer medium in the area of the heat coupling area 36, a capillary delivery pressure is generated, by which the liquid second heat carrier medium flows back from the heat decoupling area 38 to the heat coupling area 36 in the inner volume area of the capillary structure element 52, which area provides essentially a second flow space area 58. The cylindrical capillary structure element 52 forms part of a flow circulation arrangement for circulating the second heat carrier medium.

A thermodynamic circulation is thus formed, which is based on the fact that there is a temperature difference between the heat coupling area 36 and the heat decoupling area 38, and this difference is present such that the temperature in the heat coupling area 36 is at or above the evaporation temperature of the second heat carrier medium and the temperature in the heat decoupling area 38 is at or below the condensation temperature of the second heat carrier medium.

Extraordinarily efficient heat transfer from the heating air L_(H) to the water contained in the water reservoir 32 is achieved in the thermodynamic circulation described above in each of the heat exchanger tubes 34. Due to the automatic termination of this thermodynamic functionality when the above-described temperature limit is reached, it is not necessary to keep ready any measures in terms of circuitry or to monitor the temperature of the water concerning the switching off of heater 12.

It shall be pointed out in this connection that the heat exchanger tubes 34 could, of course, have another configuration as well. The capillary structure element 52 could, of course, also be arranged with another configuration in space in the inner volume of a heat exchanger tube 34. The heat exchanger tubes 34 could also form a flow circulation arrangement for circulating the second heat carrier medium and operate without the capillary structure element 52 according to the so-called thermosiphon principle, in which the delivery between the heat coupling area 36 and the heat decoupling area 38 takes place by the action of the force of gravity. However, this requires a correspondingly defined orientation of the heat exchanger tubes 34 in respect to the direction of the force of gravity.

However, it is significant that regardless of the design or principle of action of the heat exchanger tubes 34, the heat coupling area 36 will always be obtained or become established where the heat exchanger tube 34 is in contact with a heat source, here the heating air L_(H). The heat decoupling area 38 will likewise always becomes established or appear where the heat exchanger tube 34 is in contact with a heat sink, i.e., the water to be heated here. This means that each heat exchanger tube 34 acts as a heat coupling area 36 with its entire area over which it extends in the heating air duct 28 and it acts as a heat decoupling area over its entire area over which it is located in the water or the water reservoir 32 and thus it actively heats the water contained therein, without special design measures being necessary for this.

FIGS. 6 through 8 show different variations concerning the embodiment or the direction of extension of the heat transfer tubes.

Thus, FIG. 6 shows an arrangement in which the heat transfer tube 34 or preferably all heat transfer tubes 34 is/are located with its/their heat coupling area 36 essentially in parallel to the direction of flow R of the heating area L_(H) in the area of the heat transfer arrangement 30. In a transition area 60, in which the heat exchanger tube 34 is bent, for example, at an angle of 90°, heat exchanger tube 34 passes over into a direction of extension essentially at right angles in relation to the direction of flow R, still within the heating air duct 28 in the exemplary embodiment according to FIG. 6, i.e., in the heat coupling area 36, and it likewise extends at right angles to the direction of flow R in the water reservoir 32 away from the heating air duct 28.

The heat coupling area 36 of the heat exchanger tube 34 or preferably of all heat exchanger tubes 34 is again located approximately at right angles to the direction of flow R in the embodiment shown in FIG. 7. The transition area 60 is located here in the interior space 40 of the water reservoir 32, i.e., in the heat decoupling area 38. The heat exchanger tube 34 extends now essentially in parallel to the direction of flow R with the essential area over which the heat decoupling area 38 extends.

Two transition areas 60, 60′ are present in the variant shown in FIG. 8. Transition area 60′ is located in the heating air flow duct 28, i.e., still in the heat coupling area 36 of the heat exchanger tube 34 shown, while transition area 60′ is located in the interior space 40 of water reservoir 32, i.e., in the heat decoupling areas 38 of the heat transfer tube 34. The essentially longitudinal sections of the heat coupling area 36 and of the heat decoupling area 38 extend essentially in parallel to one another here and also in parallel to the direction of flow R. Consequently, there is an essentially U-shaped configuration of the heat exchanger tubes 34, whereas there is an essentially L-shaped configuration in the embodiments according to FIGS. 6 and 7. However, the bend formed in a particular transition area 60 and 60′ is always close to the area in which the heat coupling area 36 adjoins the heat decoupling area 38. It is obvious that more bent or transition areas, in which the heat transfer tube may be bent, may be also be provided farther from this junction area.

To obtain the most uniform heating characteristic possible over the entire volume of water reservoir 32, it is, of course, possible to combine different directions of extension especially of the heat decoupling areas 38 of different heat exchanger tubes 34. Since the warmer water will accumulate, based on the force of gravity, in the upper area, i.e., for example, the area of the water reservoir 32 located farther away from the heating air duct 28, it can nevertheless be ensured that a larger total surface of the heat decoupling areas 38 of different heat exchanger tubes 34 is provided in the lower volume area of the water reservoir 32, i.e., for example, in the volume area located closer to the heating air duct 28.

While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles. 

1. A water heater system comprising: a heater comprising a heat exchanger arrangement for transferring heat made available in said heater to a first heat carrier medium; a water reservoir for receiving water to be heated; and a heat transfer arrangement for transferring heat being transported in the first heat carrier medium to water in said water reservoir, said heat transfer arrangement comprising a heat exchanger tube with a heat coupling area that is or can be brought into thermal interaction with the first heat carrier medium and with a heat decoupling area that is in thermal interaction with water in said water reservoir, wherein a second heat carrier medium is contained in said heat exchanger tube and said heat exchanger tube has a first flow space area for essentially gaseous second heat carrier medium flowing from said heat coupling area to said heat decoupling area and a second flow space area for essentially liquid second heat carrier medium flowing from said heat decoupling area to said heat coupling area.
 2. A water heater system in accordance with claim 1, further comprising: a heat carrier medium duct from said heat exchanger arrangement to said heat transfer arrangement; and a flow delivery arrangement for delivering said first heat carrier medium from said heat exchanger arrangement through said heat carrier medium duct to said heat transfer arrangement.
 3. A water heater system in accordance with claim 2, wherein said flow delivery arrangement comprises a heating air blower.
 4. A water heater system in accordance with claim 1, wherein said heat exchanger tube extends at least in said heat coupling area essentially at right angles to a direction of flow of the first heat carrier medium in the area of said heat transfer arrangement.
 5. A water heater system in accordance with claim 1, wherein at least a portion of said heat coupling area of said heat exchanger tube extends essentially in parallel to a direction of flow of the first heat carrier medium in an area of said heat transfer arrangement.
 6. A water heater system in accordance with claim 1, wherein said heat exchanger tube extends essentially straight over an entire length thereof.
 7. A water heater system in accordance with claim 1, wherein said heat exchanger tube is bent at least in a transition area.
 8. A water heater system in accordance with claim 1, wherein: said heat transfer arrangement further comprises additional heat exchanger tubes to provide plurality of heat exchanger tubes; and said plurality of heat exchanger tubes extend in parallel to one another at least in some areas.
 9. A water heater system in accordance with claim 8, wherein at least some of said heat exchanger tubes are offset, in relation to one another with respect to said heat coupling area thereof in a direction of flow of the first heat carrier medium in an area of said heat transfer arrangement and/or at right angles thereto.
 10. A water heater system in accordance with claim 1, wherein the second heat carrier medium has a condensation temperature in the range of 60° C. in at least one heat exchanger tube.
 11. A water heater system in accordance with claim 1, wherein said heater comprises a burner for receiving fuel and combustion air and for burning a fuel/combustion air mixture.
 12. A water heater system in accordance with claim 1, wherein said second flow space area is provided with material having a capillary structure at least in some areas.
 13. A water heater system comprising: a heater comprising a heat exchanger arrangement for transferring heat made available in said heater to a first heat carrier medium; a water reservoir for receiving water to be heated; a heat carrier medium duct; a heat transfer arrangement, said heat carrier medium duct extending from said heat exchanger arrangement to said heat transfer arrangement for transferring heat, via said first heat carrier medium, from said heat exchanger arrangement to said heat transfer arrangement, said heat transfer arrangement comprising a heat exchanger tube enclosing a space with a heat coupling area for thermal interaction with the first heat carrier medium and with a heat decoupling area for thermal interaction with water in said water reservoir and a flow circulation arrangement for circulating a second heat carrier medium contained in said space and enclosed by said heat exchanger tube, said heat exchanger tube having a first flow space area for essentially gaseous second heat carrier medium flowing from said heat coupling area to said heat decoupling area and having a second flow space area for essentially liquid second heat carrier medium flowing from said heat decoupling area to said heat coupling area; and a flow delivery arrangement for delivering said first heat carrier medium from said heat exchanger arrangement through said heat carrier medium duct to said heat transfer arrangement.
 14. A water heater system in accordance with claim 13, wherein: said heater comprises a burner for receiving fuel and combustion air and for burning a fuel/combustion air mixture; and said flow delivery arrangement comprises a heating air blower.
 15. A water heater system in accordance with claim 13, wherein said heat exchanger tube is bent at least in a transition area; and one of: at least a portion of said heat coupling area of said heat exchanger tube extends essentially at right angles to a direction of flow of the first heat carrier medium in the area of said heat transfer arrangement; and at least a portion of said heat coupling area of said heat exchanger tube extends essentially in parallel to a direction of flow of the first heat carrier medium in an area of said heat transfer arrangement.
 16. A water heater system in accordance with claim 13, wherein said heat exchanger tube extends essentially straight over an entire length thereof.
 17. A water heater system in accordance with claim 13, wherein: said heat transfer arrangement further comprises an additional heat exchanger tube to provide plurality of heat exchanger tubes; and said plurality of heat exchanger tubes extend in parallel to one another at least in some areas.
 18. A water heater system in accordance with claim 17, wherein at least some of said heat exchanger tubes are offset, in relation to one another with respect to said heat coupling area thereof in a direction of flow of the first heat carrier medium in an area of said heat transfer arrangement and/or at right angles thereto.
 19. A water heater system in accordance with claim 13, wherein the second heat carrier medium, contained in said in heat exchanger tube, has a condensation temperature in the range of 60° C.
 20. A water heater system in accordance with claim 13, wherein said flow circulation arrangement comprises a material having a capillary structure at least in some areas, said material being provided in said second flow space area. 